How many hours can the average helicopter (the one I have in mind would seat around 6 people - could be military or commercial - preferably commercial) stay in the air for?
25 hours, max.
The Robinson R22, a fairly popular small chopper must be inspected every 100 hours of TIS - “time in service” for airframe defects, as well as engine service (oil change) at 100 hours. There are also some flight control checks to be done every 25 hours TIS - some of their cyclics have been found to wear out and jam, so they get a good looking at pretty often. Failure here leads to inability to control the helicopter.
These intervals aren’t unique to the Robbos - Some Bell (Some of their models you may recognize are the Jet Ranger and the US Army’s UH-1, popularly called the Huey.) helicopters also have a 25-hour TIS inspection requirement - the rotor blades are to be washed and gone over with a magnifying glass to look for cracks.
So, even if you could arrange for mid-air fueling, most helicopters are legislatively restricted to no more than 25 hours running time so they can be inspected for cracks and damage to the rotors that could lead to catastrophic failure, or damage to the controls, which could lead to the helicopter taking on the aerodynamic qualities of a rock.
And how long can your average chopper stay in the air for on one tank of fuel?
This site has a list of different helicopters with specifications. The endurance is around 3.5 to 4.5 hours for most of them.
Note that the times given are for “no reserve”. I’m not sure of the legal requirements for reserve fuel in helicopters but I think you could take at least thirty minutes off for resverves.
Brilliant. Thanks, all. In a children’s book I’m working on (editing, improving…) I’d written of a 5-hour journey. May lop an hour off just in case any doperkid gets hold of the book and Pits it.
They can’t stop for gas?
The H-60 (comparable to the civilian S-70) can fly for about 3.5 hours and land with a reasonable reserve. (At least that’s true for the Navy’s SH-60B) Most H-60’s can also carry one or two auxiliary tanks that hold about another hour or so of fuel each, so a 5-hour trip with aux tanks should be no problem.
Some have IFR - in flight refueling - probes so they don’t even have to stop. And strictly speaking it would be for jet fuel. I don’t know of any gasoline powered helecopters that have an IFR probe.
Hey, what kind of range would those 4-6 hour flight times work out to?
Reason I ask, is I remember playing Jane’s Fleet Command and constantly being frustrated that I couldn’t keep my ASW helicopters in play for as long as I would have liked without refueling. That’s as opposed to my jet fighters, which always got to the target, ran out of ammo, and came back generally having fuel to spare.
For an H-60, max range airspeed at sea level is about 125 knots. With a full tank (~4000 lbs of fuel), that winds up being in the ballpark of 400 nm range.
Keep in mind that for a helicopter, max range and max endurance airspeeds are often quite different. Again for an H-60, flying 55 knots or so will let you squeeze a lot more time out of a given fuel load (though not getting as far as if you flew faster but for less time). For game (and real life) purposes, you want your helos to dash to where they need to be and then slow down to max endurance airspeed.
I just did a quick look at cruise speeds for some common helicopters.
R22 75 kts
Jet Ranger 100 kts
BK117 133 kts
Westland Lynx 137 kts
Helicopters are very cool machines but they are, in general, slow and therefore somewhat limited in range. The BK117 which is often used for aeromedical work in this part of the world has a range of 292nm with no reserves. Basically, if you want to GET somewhere, you use an aeroplane. If, on the other hand, you need to do a specific task such as rescue some sailors off a sinking yacht or land a critical patient on the top of a hospital, you use a helicopter.